Novolak/diazonaphthoquinone (DNQ) resists have been the most widely used photoresists in the manufacture of microelectronic devices such as semiconductors since their introduction in the 1960's. However, the ever increasing demand for high resolution imaging has driven the microlithography industry towards the use of short wavelength radiation, which is not suitable for DNQ resists. In general, these radiation sources have much lower output power than the conventional 360 nm or 435 nm mercury emission lines. The resist materials that have been designed for use with conventional sources are noncatalytic in nature and their use in combination with the lower power radiation sources leads to a drop in throughput as the time required for exposure of each wafer increases. In order to alleviate this problem, resists with much higher sensitivities have been developed. One approach to increasing the sensitivity is the use of a chemically amplified system, such as the acid-catalyzed thermolysis of t-butyloxycarbonyloxy (tBOC) protected poly(4-hydroxystyrene). See, J. M. J. Frechet, et al., Polymer 24:995 (1983). The increased sensitivities of these catalytic imaging materials relative to conventional DNQ resists has enabled the implementation of deep-UV lithography and also contributed to advances in electron beam lithography.
In the last decade, a large number of new imaging materials based on chemical amplification have been designed. Most of the modifications containing t-BOC or t-butyl ester active groups afford either positive or negative-tone images as a function of the choice of developer. Alternatively, crosslinking through electrophilic aromatic substitution followed by aqueous base development has been used to create negative-tone resists that afford non-swollen images.
There remains a need in the art for photoresists having both high resolution and high sensitivity. There also remains a need in the art for photoresists which are useful in deep-UV image resolution techniques. Moreover, there remains a need in the art for photoresist crosslinking agents capable of providing high resolution and sensitivity photoresists.